Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$137.31	10.696%	$151.9967	$152.00	$152.00	$152.00
Purchase #2	$47.94	9.631%	$52.5571	$52.56	$52.55	$52.60
Purchase #3	$250.29	4.356%	$261.1926	$261.19	$261.20	$261.20
Purchase #4	$80.95	5.336%	$85.2695	$85.27	$85.25	$85.30
Purchase #5	$188.39	12.216%	$211.4037	$211.40	$211.40	$211.40
Purchase #6	$63.65	10.351%	$70.2384	$70.24	$70.25	$70.20
Purchase #7	$55.58	7.399%	$59.6924	$59.69	$59.70	$59.70
7 purchase totals =	$824.11		$892.3504	$892.35	$892.35	$892.40